There are four pictures in the Wingleader book: two on p.11, one on p.12 and one on p.13. The main picture on p.11 shows a lineup of 15 of 48 Squadron's aircraft at Manston shortly after the Squadron's formation on 6 March 1936, from which it appears that the aircraft bore no squadron markings apart from an individual aircraft letter. Discernable markings include K6158/E, K6173/C and K6182, which could be either X or Y. That picture, and the one with it, also show the early-delivery aberration of serials being displayed above the wings. On p.12 there is a picture of K8732/A described as "serving with the School of Air Navigation"; the two on p.13 are of L7046/E1 and L7046 Q1, both School of Air Navigation aircraft. All pictures show the standard pre-war overall silver finish, with polished metal cowls.
Edit: Sabrejet's picture above is another from what must have been a series taken on the same day; it is apparent from that picture that K6173 is in fact "G".